This invention relates to air locks, and to the power operation of doors for air locks in a manner which maintains the security of the enclosures protected by the air locks. An aspect of the invention is the use, in an air lock, of door closer apparatus of the general type described in U.S. Pat. No. 4,222,147, issued Sept. 16, 1980, to L. Nelson Burnett, and assigned to the assignee of the present invention. In that patent, apparatus was described in which the operation of a door was achieved by means of a hydraulic door closer, overbalanced by a pneumatic actuator physically associated with the closer. In that patent and elsewhere it was proposed that such an opener be controlled by a remotely manually operable valve, such as a palm button mounted on a wall adjacent to the door, or by means responsive to initial displacement of the door (by manual pressure against the door) to override in whole or in part the closing bias of the door closer.
Apparatus for power-assisted opening of a door, with spring-urged closing, has heretofore been proposed. See, for example U.S. Pat. No. 2,190,653, issued Feb. 20, 1940 to Andrew C. Dunn, and U.S. Pat. No. 3,478,468, issued Nov. 18, 1969, to Paul W. Martin. In the Martin patent, a hydraulic door operating system was proposed in substitution for the familiar hydraulic door closer.
In certain situations, it is desirable that more than one door or door closer be operated in interrelated fashion to achieve a desired result. Air locks, for example, are intended to prevent the passage of air into or out of a protected enclosure, usually a room or enclosure in which a controlled atmosphere is essential to the activity to be carried on within the protected enclosure. For example, in a biological laboratory in which experiments or operations are conducted which relate to biologically dangerous agents, it is essential that the possibility of contamination of areas adjacent to the enclosure be eliminated. The use of an air lock is one helpful technique for doing so. Similarly, in certain biological experiments it is essential that the possibility of contamination from outside the enclosure be avoided. Here too, an air lock is useful. In the electronics industry, where it is sometimes necessary to grow pure crystalline substance and to assemble electronic components in so-called "clean" rooms, air locks are also useful.
Typically, an air lock consists of a chamber or vestibule, closed at respective ends by a pair of individually operable doors. In passing into the protected enclosure, the outer door is first opened to permit entry into the chamber or vestibule. The outer door is then closed, and the inner door opened for entry into the protected area. In leaving the protected enclosure, the sequence of operation of the doors is reversed. In some applications, the air in the chamber or vestibule is purged at an intermediate point in the process during which both doors are closed, and the present invention allows for this as well.
It is the principal object of this invention to provide an air lock and door operating apparatus for an air lock wherein operation of one of the doors may be initiated by initial opening displacement of the door or, alternatively, by manually operable remote switch means, and wherein the opening of the first door causes the second door to be latched against opening while the first door is opened. The latch means, however, in the preferred embodiment of the invention, may be overridden for safety purposes. Also, in the preferred embodiment, associated with the control system for the doors is a means for triggering air handling apparatus (which, per se, is not a part of the present invention) associated with the chamber or vestibule.
Other objects will appear hereinafter.